Lidar Observations at 0.7 Micrometers and 10.6 Micrometers Wavelengths during Smoke Week II

摘要

A 10.6 micron wavelength lidar was operated by the U.S. Army Atmospheric Sciences Laboratory and a 0.7 micron wavelength lidar (Mark IX) was operated by SRI International to observe smoke and dust clouds generated during Smoke Week II at Eglin AFB from 6 through 16 November 1978. The lidars observed cloud backscatter along horizontal paths that were nearly coincident with those observed by visible and infrared transmissometers operated by the Dugway Proving Ground. The lidar observed paths were terminated with a passive reflector so that time-dependent transmission over the lidar-to-target path could be evaluated from lidar observed target returns. Backscatter signatures for both lidars were digitized and recorded on magnetic tape using the Mark IX lidar data processing system. Recorded lidar data were used to generate intensity-modulated TV displays depicting cloud structure along lidar observed paths as a function of time. These displays were used to choose sixteen Smoke Week II trials for quantitative analysis in terms of cloud attenuation and path-integrated backscatter. Transmissions derived from lidar target returns agreed very well with transmissometer records, except for phosphorus events for which the lidar values were greater by as much as an order of magnitude. This discrepancy can be explained because the transmissometer paths were nearer to the surface than the lidar paths and other observations indicated that phosphorus clouds greatly decrease in optical density in the vertical.